The present invention relates to an improved soundboard for musical instruments, and more particularly to an improved construction of a laminated soundboard used for stringed musical instruments such as pianos.
In producing the acoustic effect of a stringed musical instrument such as a piano, a soundboard plays a very important role in amplifying the vibration of the strings and the generation of the musical tones. The operational characteristics of the soundboard have a great influence on tone quality and volume and the envelope of musical tones generated by the piano. It can be safely said that the soundboard is a key factor in determining the quality of performance of a piano.
To exhibit high performance characteristics, a soundboard is required to have low specific gravity, highly elastic behavior, little absorption of vibration energy, and uniform resonance characteristics from the bass to the treble range.
Woods such as silver fir or spruce have been used for the production of soundboards. The use of such natural materials, however, leads to high production costs and complicated manufacturing steps. In addition, since the modular ratio, E/.rho. or specific Young's modulus, i.e., the value of Young's modulus of a material divided by the density of the material of the soundboard being manufactured, is unavoidably restricted to the values special to woods, there is an inherent limit to the capacity of the wooden soundboard to generate musical tones.
In order to avoid the expenses and limitations of wooden soundboards, laminated soundboards have been proposed which utilize a core material of low specific gravity such as foam plastic upon which is bonded wooden face plates. Soundboards of this construction, however, due to the low shearing elastic modulus (G) of the core and large shearing loss tangent, exhibit poor sound production at high frequencies, low tone volume, and as a result, a poor envelope of musical tones is generated. Thus, no beautiful tonal balance can be expected. The shearing loss tangent is the measure of energy lost in the conduction of shearing deformations generated at a certain frequency through a soundboard. The shearing loss tangent is a measure of the attenuation of energy or the damping effect of the conducting media on vibrations of a certain frequency. The shearing loss tangent is equal to the ratio of shearing loss modulus with respect to shearing storage modulus.
Laminate soundboard constructions using wood for the core also exhibit relatively low modular ratio and large internal loss, and thus share the poor quality sound production characteristics of plastic core soundboards known in the art.